Purification of 2, 2, 2-trifluoro-1-chloro-1-bromoethane



United States Patent "ice 3,388,175 PURIFICATION OF 2,2,2-TRlFLUORO-1- CHLORO-l-BROMOETHANE David John Viney, Rnneorn, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Dec. 20, 1965, Ser. No. 515,248 Claims priority, application Great Britain, Jan. 1, 1965, 55/65 Claims. (Cl. 260653) ABSTRACT OF THE DISCLOSURE There is provided a process for the purification of 2,2,2- trifiuorod-chloro-l-bromoethane, commonly known as halothane, wherein impurities of the formulae and CF =CClZ wherein X is hydrogen bromine or chlorine, Y is bromine or chlorine and Z is hydrogen, bromine, chlorine and fluorine are removed. The halothane while in the liquid state is purified by contacting the halothane with a solution of a metal permanganate which removes the said impurities.

This invention relates to a purification process and more particularly it relates to a process for the purification of 2,2,2-trifluoro-1-chloro-l-bromoethane hereinafter referred to as halothane.

Halothane is a valuable inhalation anaesthetic used for the production of anaesthesia in men and in animals. However, depending on the manner of manufacture of halothane, it may contain small amounts of certain impurities and it is an object of the present invention to remove such impurities.

According to the present invention we provide a process for the purification of impure halothane containing as impurity at least one compound of the formula CF CX=CY CF wherein X stands for hydrogen, bromine or chlorine and Y stands for bromine or chlorine and/or at least one compound of the formula CF =CClZ where Z is hydrogen, bromine, chlorine or fluorine which comprises intimately contacting said impure halothane in the liquid phase with a metal permanganate and recovering the purified halothane.

It is to be understood that any compound of the abovestated formula CF -CX:CY-CF may be present as impurity in the form of a cis isomer or a trans isomer or a mixture thereof.

The permanganate treatment can be carried out .using aqueous, non-aqueous solvents, particularly organic solvents (for example acetone), or mixtures of such solvents, which are not appreciably attacked by permanganate. The use of organic solvents can increase the rate of attack on the impurities in the halothane but can also complicate subsequent isolation of the purified halothaue, however, so it is generally preferred to use the permanganate in the form of an aqueous solution.

The relative proportions of halothane and aqueous solution may be varied considerably, and the optimum proportions in any particular circumstances will depend upon such factors as the thoroughness of mixing, the particu- 3,388,175 Patented June 11, 1968 lar impurities present and the amounts of these which have to be removed, and the temperature of treatment. Suitable proportions are in the range 1:5 to 5:1 by volume, though proportions outside this range may be used if desired. Proportions of about 1:1, i.e. approximately equal volumes of halothane and aqueous solution, are usually found to be suitable and convenient.

The permanganate may be in particular an alkali metal or alkaline earth metal permanganate, and the permangnate solution may be acid, neutral or alkaline. Of the latter a neutral or alkaline solution is perferred. If the solution is to be alkaline, this may be achieved most conveniently by addition of an alkali metal hydroxide, though other bases may be used if desired, for example, alkaline earth metal hydroxides or ammonia. If the solution is to be acid, this may be conveniently achieved by addition of, for example, sulphuric acid.

Useful results can be obtained when using up to 10% by weight in the aqueous phase of sodium hydroxide or potassium hydroxide although higher concentrations than this could be used if desired. However lower rather than higher proportions than 10% by weight of NaOH or KOH are preferred and it is particularly preferred to employ concentrations of up to 2% by weight NaOH or KOH, for example 0.1% to 2% by weight NaOH, in the aqueous phase.

Sodium and potassium permanganates are particularly useful metal permanganatcs to be used in the process of the invention. Useful results may be obtained with various concentrations of permanganate in the aqueous phase. For example, good results are obtained when using a substantially saturated solution of potassium permanganate in the aqueous phase, that is about 60 g./l. potassium permanganate at ambient temperature.

Preferably the inpure halothane is vigorously agitated with the aqueous solution of the permanganate. Thus in one suitable method the impure halothane is vigorously agitated with an aqueous solution of the permanganate at a temperature ranging from 0 C. to the boiling point of the mixture, for example, at ambient temperature, the agitation is stopped and the mixture is allowed to separate into two distinct layers, and the lower halothane layer is fractionally distilled.

The process may be carried out in a batch or continuous manner. Again the present process may be used in comjunction with other purification procedures, for example, those based on fractional distillation which can be carried out before or after the present process.

The following example illustrates but does not limit the invention. All parts are to be read as parts by weight.

Example l-chloro-l-bromo-2,2-difluoro ethylene. l-chloro-2,2-difluoro ethylene.

Halothane Iermanganate Solution Total Tempera- Time, Impurities, Impurities Permanganate Water, Additive ture, 0. hours Remaining, Parts present Parts p.p.m.

Cation Parts Compound Parts 100 50p.p.m.C Ca 5 50 Nil Nil 22 2 5 145 95p.p.m.g. K 4.5 75 NaOH 1.5 1.5

35 p.p.m. :s g K 3 100 His/0 2 4s 3 5 0p.p.m. i r 23 K a 100 NHi 1 2a 2.5 5

p.p.m. 1 1 gg g Ba 4 100 135(011 z 22 2.5 5 p-p- T F go A 1 5 108 KOH 0.5 50 1 5 p.p.n1. ls5p p mho K 155 4,250 NaOlI s5 1 5 100 p.p.m. C 170 p.p.m. 210 ppmD Ba 5 54 NaOH 1 21 8 5 150 ppm. EH ppm. 251.... p.p.m. zlop'pJmDnn NA 4 10s NaOll 2 :1 7 5 150 ppm. E...

p.p.m. K 14,000 300,000 NaOII 4,000 27 5.5 10 110 p.p.m. E 75 p.p.m. G K 4 100 NaOH 1.5 22 0.25 5 05 p.p.rn. K 1.5 27 NaOH 0.5 21 0.75 5 70 p.p.m. A 375 p.p.m. C 725 p.p.m.D NA 10 100 NaOH 2 50 5 5 620 p.p.m. E p.p.m. F 385 p.p.mBA. a

p.p.m 125 ppm K 12,315 300,000 NaOH 4,870 22 2 5 75 p.p.m F"...

What I claim is: 30 potassium permanganate is employed as the metal per- 1. A process for the purification of impure 2,2,2-trimanganate. fluoro-l-chloro-bromoethane containing as impurity at 7. A process as claimed in claim 6 in which a substanleast one compound selected from the group consisting of tially saturated solution of potassium permanganate in the a compound of the formula CF -CX=CYCF whereaqueous phase is employed. in X stands for hydrogen, bromine or chlorine and Y 8. A process as claimed in claim 1 in which the purificastands for bromine or chlorine and a compound of tion process is carried out at ambient temperature. the formula CF =CClZ where Z is hydrogen, bro- 9. A process as claimed in claim 2 in which the relative mine, chlorine or fluorine and mixtures thereof, which proportions of 2,2,2-trifluoro-1-chloro-l-bromoethane to comprises intimately contacting said impure 2,2,2-t1'iaqueous solution of permanganate is in the range 1:5 to fiuoro-l-chloro-bromoethane in the liquid phase with 5:1 by volume. solution of a metal permanganate, at a temperature from 19, A process as l i d i l i 1 hi h comprisgs about Q P to h bolllng P of the mlxture and vigorously agitating the impure 2,2,2-trifiuoro-l-chlororefowrmg the Punfiad bromoethane with an aqueous alkaline solution of the per- Ct a 1 1 h a u Gus manganate at a temperature ranging from 0 C. to the procbss as c alme C mm W 1c an q 6 boiling point of the mixture, stopping the agitation and solution of the metal permanganate is employed.

allowing the mixture to separate into two distinct layers, 3. A process as claimed in claim 2 in which the soluand fractional] distimnn the IOWC 2 2 2 trifiuoro 1 tion is neutral or alkaline. chlorobromo la D 1 4. A process as claimed in claim 3 in which up to 10% e by weight sodium or potassium hydroxide is present 1n the References Cited aqueous phase.

5. A process as claimed in claim 4 in which up to 2% UNITED STATES PATENTS by weight sodium or potassium hydroxide is present in the 2,999,885 9/1961 Heberling 260-653 aqueous phase.

6. A process as claimed in claim 1 in which sodium or 5 DANIEL D. HORWITZ, Primary Examiner. 

